Inductor

ABSTRACT

An inductor is arranged such that the projection area of each terminal portion falls within a square circumscribing the projection area of an upper flange portion under a state where the inductor is projected orthogonally in the direction of the axis. Projection area of each end of a winding connected to the joint of the terminal portions also falls within the square. Consequently, an installation space can be secured easily on a board, and a space saving inductor in which a space for installation of other components can be secured easily on the periphery can be obtained.

TECHNICAL FIELD

The present invention relates to an inductor having a drum core aroundwhich a winding is wound and a terminal portion formed by a metal platemember securely fixed to the drum core. In particular, it relates to aninductor suitable for use in a power supply circuit of an electronicdevice that is highly required to be downsized (or slimmed down), suchas a cellular phone, a portable music player, a portable video gamemachine and a compact camcorder.

BACKGROUND ART

A known inductor of this type is described in the patent document listedbelow. The inductor described in the patent document has smallstrip-shaped protrusions that are formed along an edge of a metal platemember (a metal piece) forming a connecting terminal portion and anelectrode portion and abut on the side surface of a lower flange portionof a drum core, and the small strip-shaped protrusions improve theprecision of positioning of the drum core and the metal plate member.

Patent document 1: Japanese Unexamined Patent Publication No. 10-22137

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Recently, electronic devices using inductors of this kind have beendownsized, and in keeping with this trend, the demand for smallerinductors used in the circuit boards of those devices has beenincreasing. In particular, in order to pack more electric (electronic)components in smaller circuit boards, a space saving inductor is neededwhich not only requires only a small installation area on the board butalso facilitates securing of the space for installation of othercomponents around the inductor.

The present invention has been made in view of such circumstances, andan object of the present invention is to provide an inductor thatfacilitates securing of a space for installation thereof on a board andsecuring of a space for installation of another component around theinductor.

Means for Solving the Problems

In order to attain the object described above, an inductor according tothe present invention comprises: a drum core that has a winding portionand roughly circular flange portions formed at the both ends of thewinding portion; a winding that is wound around the winding portion; anda terminal portion being formed by a metal plate member and beingsecurely fixed to an end face of one of the flange portions and has ajoint to which an end of the winding is connected and a mounting part atwhich the inductor is mounted on a board, and characterized in that, inthe orthogonal projection of the inductor in the direction of an axis ofthe winding portion, the projection area of the terminal portion atleast falls within a square that circumscribes the projection area ofthe flange portion of the flange portions that has a larger or equaldiameter.

The inductor according to the present invention is preferably configuredso that, in the orthogonal projection, the projection area of a solderfillet formed by soldering of the terminal portion to the board fallswithin the square.

In the inductor according to the present invention, the flange portionscan have the same outer dimensions.

EFFECT OF THE INVENTION

Since the inductor according to the present invention is configured sothat, in the orthogonal projection of the inductor in the direction ofan axis of the winding portion, the projection area of the terminalportion at least falls within a square that circumscribes the projectionarea of the flange portion of the flange portions that has a larger orequal diameter, the installation space of the inductor on the board islimited to within the predetermined square area. Therefore, comparedwith conventional inductors whose installation spaces are not limited towithin a square area, the space for installation of the inductor can beeasily secured on the board, and another component can be efficientlyand compactly arranged in the area around the predetermined square area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an inductor according to an embodimentviewed from the front side;

FIG. 2 is a front view of a drum core shown in FIG. 1;

FIG. 3 is a perspective view of terminal portions shown in FIG. 1 viewedfrom the rear side;

FIG. 4 is a perspective view showing the terminal portions securelyfixed to the drum core viewed from the bottom side;

FIG. 5 is a plan view of the inductor according to the embodiment; and

FIG. 6 is a plan view of an inductor according to another embodiment ofthe present invention.

DESCRIPTION OF SYMBOLS

1, 1A inductor

2 drum core

3 winding

4A-4D terminal portion

5 square

6 solder fillet

21 winding portion

22 upper flange portion

23 lower flange portion

41 joint

42 mounting part

43 claw part

C1 axis

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, inductors according to embodiments of the presentinvention will be described in detail with reference to the accompanyingdrawings. FIGS. 1 to 5 show an inductor according to an embodiment ofthe present invention, and FIG. 6 shows another embodiment. In thefollowing description, the direction of the X axis of thethree-dimensional orthogonal coordinate system shown in FIG. 1 will bedescribed as the back-and-forth direction (the arrow points to thefront), the direction of the Y axis will be described as the horizontaldirection (the arrow points to the right), and the direction of the Zaxis will be described as the vertical direction (the arrow points tothe top). The three-dimensional orthogonal coordinate systems shown inthe remaining drawings have the same coordinate axes as that shown inFIG. 1.

First, with reference to FIGS. 1 to 4, a configuration of an inductoraccording to an embodiment of the present invention will be described.FIG. 1 is a perspective view showing a configuration of the whole of aninductor according to an embodiment of the present invention, viewedfrom the front side. FIG. 2 is a front view of a drum core shown inFIG. 1. FIG. 3 is a perspective view of terminal portions shown in FIG.1, viewed from the rear side. FIG. 4 is a perspective view showing theterminal portions securely fixed to the drum core, viewed from thebottom side.

An inductor 1 according to this embodiment is used in a power supplycircuit of an electronic device, such as a cellular phone, a portablemusic player, a portable video game machine and a compact camcorder, andcomprises a drum core 2, a winding 3, and a pair of terminal portions 4Aand 4B, as shown in FIG. 1.

As shown in FIG. 2, the drum core 2 integrally comprises a columnarwinding portion 21 around which the winding 3 (see FIG. 1) is wound, andcircular flange portions (an upper flange portion 22 and a lower flangeportion 23) formed at the upper and lower ends of the winding portion 21(in other words, the both ends in the direction of the axis C1 of thewinding portion 21). For example, the drum core 2 is made of softmagnetic ferrite (alternatively, the drum core 2 can be made ofpermalloy, sendust, iron carbonyl, or a dust core formed by compressionmolding of fine powder of these materials). The upper flange portion 22and the lower flange portion 23 have the same outer dimensions.

As shown in FIG. 3, each terminal portion 4A, 4B is formed by a metalplate member and has a joint 41 to which an end of the winding 3 (seeFIG. 1) is connected, a mounting part 42 at which the terminal portionis mounted on a circuit board (not shown), and a pair of claw parts 43that extend from one side edge of the mounting part 42 and are bentupward. As shown in FIG. 4, the joint 41 and the claw parts 43 of eachterminal portion 4A, 4B protrude beyond the side surface of the lowerflange portion 23, and each terminal portion 4A, 4B is securely fixed tothe bottom surface of the lower flange portion 23 by an adhesive appliedbetween the upper surface of the mounting part 42 and the bottom surfaceof the lower flange portion 23.

In the state shown in FIG. 4, which shows the terminal portions 4A, 4Bsecurely fixed to the lower flange portion 23, one end part of the joint41 is bent to the front. However, when or after an end of the winding 3is connected to the joint 41, the bent part is deformed to extend upwardas shown in FIG. 1.

The inductor 1 thus configured is mounted on a circuit board (not shown)with the bottom surface of the lower flange portion 23 facing thecircuit board as shown in FIG. 1 and fixed to the circuit board bysoldering the claw parts 43 of the terminal portions 4A, 4B to thecircuit board surface. Whether the soldering is properly achieved or notcan be confirmed by visually checking the state of the solder fillets(not shown) formed between the claw parts 43 and the circuit boardsurface.

Now, main characteristics of the inductor 1 will be described withreference to FIG. 5. FIG. 5 is a plan view of the embodiment of thepresent invention (in other words, a diagram showing an orthogonalprojection of the inductor 1 in the direction of the axis C1).

As shown in FIG. 5, the inductor 1 is designed so that the projectionarea of each terminal portion 4A, 4B falls within a square 5 (shown bythe chain double-dashed line in the drawing) that circumscribes theprojection area of the upper flange portion 22 (or the lower flangeportion 23) in the orthogonal projection of the inductor 1 in thedirection of the axis C1. In addition, the projection areas of the endsof the winding 3 connected to the joints 41 of the respective terminalportions 4A, 4B fall within the square 5.

Thus, the footprint of the inductor 1 on the circuit board (not shown)is limited to within the square 5. Accordingly, the space for installingthe inductor 1 can be easily secured on the circuit board, and anothercomponent can be efficiently and compactly arranged in the peripheralarea of the square 5.

Now, an inductor according to another embodiment of the presentinvention will be described with reference to FIG. 6. FIG. 6 is a planview of the inductor according to this embodiment of the presentinvention. In the embodiment shown in FIG. 6, components that are thesame in concept as those shown in FIGS. 1 to 5 are denoted by the samereference numerals as those in FIGS. 1 to 5, and detailed descriptionsthereof will be omitted.

An inductor IA shown in FIG. 6 comprises a drum core 2, a winding 3 anda pair of terminal portions 4C, 4D. A characteristic of the inductor IAconsists in the configuration of each terminal portion 4C, 4D.Specifically, as shown in FIG. 6, the inductor 1A is designed so thatthe projection area of each claw part 43 of each terminal portion 4C, 4Dis located in an inner area of the square 5 compared with that of theinductor 1 in the orthogonal projection of the inductor 1A in thedirection of the axis C1. As a result, the projection area of a solderfillet 6 formed by soldering of each claw part 43 to a circuit board(not shown) also falls within the square 5.

Thus, the footprint of the inductor 1A on the circuit board includingthe solder fillet 6 is limited to within the square 5. Accordingly,compared with the inductor 1 described earlier, the space for installingthe inductor 1A can be easily secured on the circuit board, and anothercomponent can be efficiently and compactly arranged in the peripheralarea of the square 5.

While inductors according to embodiments of the present invention havebeen described, the present invention is not limited to the inductorsaccording to the embodiments described above, and various modificationscan be made thereto.

For example, while the upper flange portion 22 and the lower flangeportion 23 of the drum core 2 have the same outer dimensions in theembodiments described above, a flange drum core having unequal diameter,which has a flange portions having different outer dimensions, can alsobe used. An inductor which has the flange drum core having unequaldiameter can be designed so that the projection area of each terminalportion at least falls within a square that circumscribes the projectionarea of the flange portion having a larger or equal diameter.

1-3. (canceled)
 4. An inductor, comprising: a drum core that has awinding portion and roughly circular flange portions formed at both endsof the winding portion; a winding that is wound around the windingportion; and a terminal portion being formed by a metal plate member andbeing securely fixed to an end face of one of the flange portions andhas a joint to which an end of the winding is connected and a mountingpart at which the inductor is mounted on a board, wherein, in anorthogonal projection of the inductor in the direction of an axis of thewinding portion, the projection area of the terminal portion at leastfalls within a square that circumscribes the projection area of theflange portion of the flange portions that has a larger diameter.
 5. Theinductor according to claim 4 wherein, in the orthogonal projection, theprojection area of a solder fillet formed by soldering of the terminalportion to the board falls within the square.
 6. The inductor accordingto claim 5 wherein the flange portions have the same outer dimensions.7. The inductor according to claim 4 wherein the flange portions havethe same outer dimensions.
 8. The inductor according to claim 4 whereinthe terminal portion has a claw part in addition to the joint and themounting part.
 9. The inductor according to claim 8 wherein at least twoclaw parts are provided and abut against a side surface of one of theflange portions of the drum core.
 10. The inductor according to claim 4wherein the flange portions of the drum core have the same diameter. 11.A method of manufacturing an inductor wherein the method comprises: awinding forming step of forming a winding around a drum core; aconnecting step of fixing an end of the winding to a joint of a windingconnecting terminal; and a bending step of bending the joint of thewinding connecting terminal in a direction parallel to a winding axis ofthe drum core.